The Gunners drew 1-1 with the French champions after Alexis Sanchez scored a late equaliser.
"The change has been made but to be fair to Ospina he was good all night," he told Sky Sports.
"It's just strange. I don't see why you take the risk. It's the hardest game they face in their first game of the competition. Go and lay down a marker.
"They've got away with it tonight but they must liven up and play their best players."